When we added generated spec descriptions to RSpec, we got a surprise second use for Matchers nearly for FREE!

With only a slight modification to Spec::Mocks, we are able to use the Matchers as Mock Argument Constraints as well. For example, #equal(obj) can now be used as an Expectation Matcher:

<code>x = 5
x.should equal(3)

=> expected 3, got 5 (using .equal?)</code>

or a Mock Argument Constraint Matcher

<code>thing = mock("thing")
thing.should_receive(:msg).with(equal(3))
thing.msg(5)

=> Mock 'thing' expected :msg with (equal 3) but received it with (5)
</code>

Thanks to Dan North for pointing me to Hamcrest when we were first discussing the new expectation mechanism. It turns out that Hamcrest and jMock already employ a similar idea in Java, in which a common set of Matchers is utilized by both projects.

This is a brand new addition, and is not yet fully baked. As of now (rev 1533), there are no special methods added for better mock syntax, but we’ll probably add things like #greater_than(n) so you can say #with(greater_than(n)) instead of #with(be > n), although that WILL work, however strange the syntax.

Trunksters: this is available as of rev 1533.

Everyone else: this will be released with rspec-0.8.0